The long-term goal of the proposed studies is to elucidate the relationship between oxidative stress, caloric intake and the aging process. Caloric or dietary restriction is widely recognized to prolong life span and delay the onset of age-associated pathologies in laboratory rodents. Although several hypotheses have been advanced, the nature of the underlying mechanisms is still unclear. The proposed investigation will attempt to determine if prolongation of life span of mice due to dietary restriction is associated with a decrease in the level of oxidative stress. The main hypothesis to be tested is that dietary restriction causes a downward shift in the steady-state level of oxidative stress, which results in a relatively slower accrual of age-associated oxidative molecular damage. The two Specific Aims of this study, designed to test the main hypothesis are: (1) determine if dietary restriction results in direct and reversible lowering of the level of oxidative stress in mice at various ages. This will reveal whether age is a factor in the imposition or reversibility of the dietary-related oxidative stress. (2) determine if dietary restriction results in long-term deceleration of age-related accumulation of oxidative molecular damage. This will indicate if the effects of dietary restriction become progressively less reversible with the increased length of dietary restriction. The level of oxidative stress will be measured in the brain, heart and kidney using a battery of tests for (a) rates of mitochondrial superoxide anion radical and hydrogen peroxide generation, (b) activities of antioxidative enzymes and accumulation/transcription of their respective mRNA's, (c) ratios of redox couples such as GSH (reduced glutathione)/GSSG (oxidized glutathione), NADPH/NADP+ and NADH/NAD+, (d) oxidative damage to DNA proteins and lipids, and (e) susceptibility of tissues to experimentally-induced oxidative stress. The novelty and significance of this study is that it will indicate if dietary restriction causes a relatively immediate decrease in the level of oxidative stress, and if this effect is reversible, and if the degree of reversibility is dependent on the duration of dietary restriction. Such information is essential in understanding the nature of the relationship between dietary restriction, oxidative stress, and aging.